DE60019169T2 - METHOD, CATALYST SYSTEM AND DEVICE FOR TREATING SULFUR-CONTAINING GAS - Google Patents

Description

Territory of invention

The present invention relates to the removal of nitrogen oxides (NO _x ) and gaseous sulfur compounds, in particular SO ₃ and H ₂ S, from gaseous streams, in particular the exhaust gas of lean combustion, internal combustion engines using a regenerable catalyst system.

State of technology

Gas desulphurization is the subject of a variety of technologies. For example, wet and dry cleaning processes have been developed in flue gas desulphurization. Dry cleaning brings the effluent medium into contact with a solid material which chemically reacts with and forms a compound with the sulfur component. The system may be a fixed bed, such as zinc oxide pellets, which are used to react with H ₂ S to form zinc sulfide. The zinc sulfide pellets must be removed after saturation and replaced. The dry cleaning may also be introduced into the stream in powder or particulate form, followed by a fabric filter or electrostatic filtration to remove the reacted product. An example of a powder would be limestone, which would react after being introduced into the exhaust stream to form calcium sulfate and / or calcium sulphate hemihydrate slurry. The material is normally supplied as a wet slurry which dries in the exhaust gas and reacts with the sulfur oxides. This material is then removed and typically deposited in a landfill. There are also regenerable dry cleaning materials such as copper oxide on alumina pellets or spheres. The regenerable copper systems must be heated to high temperatures or reduced in these. This method requires that the sorption temperature be lower than the regeneration temperature.

wet Cleaning procedures use wet slurries or amine solutions and require that the exhaust gas temperature below the boiling point of too using solutions is reduced. These methods lead to losses due to evaporation and entrainment and produce products that are contaminated and unused can be and must therefore disposed of and / or cleaned before reuse.

diesel engines generate high levels of nitrogen oxides, carbon monoxide, unburned Hydrocarbons from fuel, sulfur oxides and carbonaceous Soot. The Carbon monoxide and unburned fuel components can be effective by an oxidation catalyst in the oxygen rich diesel exhaust environment be removed. The nitrogen oxides, however, make a special Problem because they require a reducing environment in order to Nitrogen to be transformed, which is a common part of the air is. Selective catalytic reduction (SCR) in the presence of excess oxygen with ammonia and hydrocarbons have been intensively studied and to a limited extent used to treat diesel exhaust. The main problem, which related to the use of SCR is that the reducing agent (Ammonia) dangerous and is toxic; it has to be stored and transported and one appreciable amount of the reducing agent is released to the environment (Ammonia slip).

The SCR process reduces NO _x but does not normally reduce carbon monoxide, hydrocarbons or sulfur oxides. The reaction of ammonia with sulfur oxides also creates particulate contaminants that can pollute the air, as well as downstream the heat transfer device.

US Pat. No. 5,451,558, which is fully incorporated herein, discloses a method of reducing the levels of NO _x , CO and SO ₂ emissions from gas turbines using a regenerable catalyst / absorber, preferably consisting of alumina / platinum / carbonate salt, to remove the contaminants Oxidize oxides and absorb them. This system is commercially used under the SCONOx brand and has been designated LAER (Lowest Achievable Emission Rate) by Department IX of the Gas Turbine EPA. Regeneration for this type of catalyst / sorber is disclosed in US Patent No. 5,599,758 at temperatures in the range of 121.1 to 398.9 ° C (250 to 750 ° F). Although the system is effective to remove gaseous sulfur compounds, the values showed that the catalyst performance with respect to NOx removal decreased with extended use. This effect results from the consumption of sorption sites by the formation of sulfur compounds on the catalyst surface, which are not destroyed during conventional regeneration.

US Patent Application SN 09 / 113,258, filed July 10, 1998, discloses a system for treating the exhaust gas of an industrial process or combustion source to capture gaseous sulfur compounds by contacting the exhaust gas with a structured carrier, for example coated a monolith with a ceramic oxide, for example, TiO ₂ , containing a noble metal component, for example, Pt and a modifier such as Cu.

WHERE 96/20044 discloses a method for regenerating a catalyst / absorber system.

US 5,665,321 discloses a method of reducing the levels of NOx, CO and SO ₂ emissions in a gas turbine.

U.S. No. 5,953,911 discloses a process, a shift reaction in a depleted catalyst / absorber system perform.

U.S. 6,037,307 discloses a system for treating a gas from a industrial process or a combustion source.

EP 0 657 204 A1 discloses a catalyst for purifying exhaust gases.

U.S. 4, 323, 544 discloses novel sorbers comprising an alumina carrier and a salt or a mixture of salt.

U.S. No. 5,762,885 discloses a device for regenerating a catalyst. Absorber.

It However, there is still a need for improved catalyst / absorber systems.

As a result, the present invention provides a method according to claim 1 available a catalyst according to claim 19 and a device according to claim 31, a method according to claim 32 and preferred embodiments as disclosed below and as in the dependent claims 2 to 18, 20 to 30 and 33 described.

It is an advantage that the present catalyst system can be used to remove gaseous NO _x and sulfur compounds from the exhaust gas of internal combustion engines, and this can be regenerated and reused. It is an advantage of the present invention that the regeneration has been used to remove the sulfur compounds which have been formed on the catalyst / sorber and the activity of the catalyst / sorber for NO _x removal is recovered. Another advantage of the present invention is a catalyst system that prevents the formation of sulfur compounds on the NO _x selective catalyst / sorber. It is particularly advantageous that the regeneration requires no other reducing agent than the engine fuel. These advantages and other advantages and features of the present invention will become apparent from the following description.

Summary the invention

An object of the present invention is a process for the removal of gaseous nitrogen oxides (NO _x ) and / or sulfur compounds, in particular SO ₃ and / or H ₂ S from gaseous streams, such as exhaust gas from internal combustion engines, comprising contacting a gaseous stream, which containing gaseous sulfur compounds and / or NO _x and flowing in a first direction, comprising a catalyst system comprising discrete beds of component (a) a catalyst / sorber comprising a noble metal catalyst component, a metal oxide upper component, a modifier consisting of oxides of Ag, Cu, Bi , Sb, Sn, As, In, Pb, Au or mixtures thereof, and component (b) a material comprising an oxidation catalyst selected from platinum, palladium, rhodium, cobalt, nickel, iron, copper, molybdenum or combinations thereof deposited on one High surface area support, an absorber material selected from a hydroxide, carbonate, Bicarbonate of an alkali or alkaline earth or mixtures thereof under conditions to effect a reduction in capacity in that system to remove and retain the sulfur and NO _x compounds; and then regenerating the catalyst system comprising contacting the catalyst system with a regeneration gas flowing in a second direction opposite to the first direction under conditions to remove the retained sulfur and / or NO _x compounds, the regeneration gas being a reducing gas wherein a portion of the capacity of the catalyst system for the removal and retention of the sulfur compounds and the NO _{x is} recovered. A preferred embodiment to takes alternating sorber and regeneration steps.

In an embodiment, in which the catalyst system has two discrete beds from the component (a) and component (b), the beds are preferably so arranged that the exhaust first with the (a) component in contact comes.

The (b) ingredient quickly removes both the sulfur and NO _x compounds, but it has been observed that the sulfur deposited on this ingredient is more difficult to remove than the nitrogen compounds, and a higher temperature is required for regeneration than for the removal of Nitrogen alone. However, the sulfur compounds are rapidly removed from the (a) component at lower temperatures. By first removing the sulfur compounds on the (a) component and preventing them from contacting the (b) component, lower regeneration temperatures can be used, while the benefit of high sulfur removal (component a) and high NO _x removal (component B) is achieved.

The regeneration gases provide a reducing environment. The reducing agents include hydrogen and hydrocarbons or mixtures of these. The hydrocarbon preferably comprises C ₁ -C ₁₂ hydrocarbons which may be used as a compound or as a mixture of compounds. The main component of the gaseous stream is an inert carrier gas, such as nitrogen, helium, argon or steam. The term "major ingredient" is used to mean greater than 50%. "Of particular importance is that both gaseous and distillate fuels, such as diesel, can be used as the reducing gas, so the fuel used by an engine can also be used used for regeneration, which is important for a non-stationary engine, such as in automobiles, trucks and railways.

The present invention also provides a catalyst system according to claim 19. In component (a), the noble metal component may comprise Pt, Pd, Rh, Ru or mixtures thereof, preferably Pt. The metal oxide sorbent component is an oxide of Ti, Zr, Hf, Ce, Al, Si or mixtures thereof. The modifier comprises an oxide of Ag, Cu, Bi, Sb, Sn, As, In, Pb, Au or mixtures thereof, preferably Cu, Ag, Bi and mixtures thereof. The purpose of the modifier is to inhibit the formation of H ₂ S during regeneration. A variety of modifiers were determined to be suitable; however, the most efficient are copper, bismuth and silver. The precious metal component is preferably present at between 0.005 to 20.0 weight percent of the catalyst / sorber, the sorbent component is preferably present at between 70 to 99 weight percent of the catalyst / sorber, and the modifier is preferably between 1 to 10 weight percent .-% of the catalyst / sorbent present. Preferably, the catalyst components may be coated on a carrier, wherein the catalyst / sorbent comprises from 1 to 50% by weight of the total weight. In a preferred (a) component, Pt comprises 0.005 to 0.05 grams per cubic centimeter of the noble metal catalyst component and a metal oxide orb constituent.

In the (b) component, the oxidation catalyst is selected from platinum, palladium, rhodium, cobalt, nickel, iron, copper, molybdenum or combinations thereof deposited on a high surface area support. Preferably, the catalytic ingredient is densely and completely coated with an absorber material selected from a hydroxide, carbonate, bicarbonate and a mixture of those of an alkali or alkaline earth or mixtures thereof. Preferably, the oxidation catalyst concentration is 0.05 to 0.6 wt% of the component, more preferably 0.1 to 0.4 wt%, for example 0.15 to 0.3 wt%. In particularly preferred catalysts, platinum, palladium, rhodium, cobalt, nickel, iron, copper, molybdenum or combinations thereof comprise 0.005 to 0.05 grams per cubic centimeter of the total oxidation catalyst and absorber material and the alkali or alkaline earth comprises 0.000005 to 0.02 Grams per cubic centimeter of total oxidation catalyst and absorber material. The preferred high surface area support is Al ₂ O ₃ , TiO ₂ , ZrO ₂ , SiO _2, or mixtures thereof.

The Catalyst components can be used as pellets, spheres, particles or in extruded form.

• A. Eine Abgasbehandlungsanordnung: Wenigstens zwei Katalysatorzonen, wobei jede Katalysatorzone ein Katalysatorsystem enthält, umfassend getrennte Betten aus (a) einem Katalysator/Sorber umfassend einen Edelmetall-Katalysatorbestandteil, einen Metalloxid-Sorberbestandteil, einen Modifikator bestehend aus Oxiden von Ag, Cu, Bi, Sb, Sn, As, In, Pb, Au oder deren Mischungen und (b) ein Material umfassend ei nen Oxidationskatalysator gewählt aus Platin, Palladium, Rhodium, Kobalt, Nickel, Eisen, Kupfer, Molybdän oder deren Kombinationen, abgeschieden auf einem Träger mit hoher Oberfläche, einem Absorbermaterial gewählt aus einem Hydroxid, Karbonat, Bikarbonat eines Alkalis oder Erdalkalis oder deren Mischungen; eine Hauptabgaseinlassleitung verbunden mit einem Abgaseinlassventil, eine separate sekundäre Abgaseinlassleitung von dem Abgaseinlassventil angrenzend verbunden mit einem Bestandteil (a) jeder der Katalysatorzonen; eine separate sekundäre Abgasauslassleitung, welche sich von jeder dieser Katalysatorzonen angrenzend an den Bestandteil (b) erstreckt und verbunden ist mit einem Abgasauslassventil, verbunden mit einer Hauptabgasauslassleitung, welche sich von dem Abgasauslassventil erstreckt, wobei ein Dampfflussweg durch jede der Katalysatorzonen durch beide getrennten Betten von dem Einlass zu dem Auslass in einer Anordnung vorhanden ist; und
• B. Eine Regenerationsanordnung umfassend: Eine Hauptregenerationsgaseinlassleitung verbunden mit einem Regenerationsgasventil, eine separate sekundäre Regenerationsgaseinlassleitung von dem Regenrationsgaseinlassventil verbunden mit jeder der Katalysatorzonen in der Nähe des Bestandteils (b); einen separaten sekundären Regenerationsgasauslass, welcher sich von jeder der Katalysatorzonen erstreckt und mit jeder der Katalysatorzonen in der Nähe des Bestandteils (a) verbunden ist; wobei jede sekundäre Regenerationsgasauslassleitung mit einem Regenerationsgasauslassventil verbunden ist und eine Hauptregenerationsgasauslassleitung, welche sich von dem Regenerationsgasauslassventil erstreckt.

A further subject of the present invention is a device comprising:

• A. An Exhaust Treatment Assembly: At least two catalyst zones, each catalyst zone containing a catalyst system comprising separate beds of (a) a catalyst / sorber comprising a noble metal catalyst component, a metal oxide sorbent component, a modifier consisting of oxides of Ag, Cu, Bi, Sb, Sn, As, In, Pb, Au or mixtures thereof and (b) a material comprising an oxidation catalyst selected from platinum, palladium, rhodium, cobalt, nickel, iron, copper, molybdenum or combinations thereof deposited on a high surface area support, an absorber material selected from a hydroxide, carbonate, bicarbonate of an alkali or alkaline earth or mixtures thereof; a main exhaust gas intake pipe connected to an exhaust gas intake valve, a separate secondary exhaust gas intake pipe from the exhaust gas intake valve adjacent to a component (a) of each of the catalyst zones; a separate secondary exhaust outlet conduit extending from each of these catalyst zones adjacent component (b) and connected to an exhaust gas outlet valve connected to a main exhaust outlet conduit extending from the exhaust gas outlet valve, a vapor flow path through each of the catalyst zones through both separate beds of the inlet to the outlet is in an array; and
• B. A regeneration assembly comprising: a main regeneration gas inlet line connected to a regeneration gas valve, a separate secondary regeneration gas inlet line from the regeneration gas inlet valve connected to each of the catalyst zones proximate to component (b); a separate secondary regeneration gas outlet extending from each of the catalyst zones and connected to each of the catalyst zones proximate to component (a); wherein each secondary regeneration gas outlet conduit is connected to a regeneration gas outlet valve and a main regeneration gas outlet conduit extending from the regeneration gas outlet valve.

Although the sulfur and NO _x components are removed from a gaseous stream by the catalyst system according to the present invention, it is not known in what form or by what mechanism the sulfur and nitrogen are combined with the catalyst components the catalyst oxidizes the carbon monoxide and the hydrocarbon contaminants to carbon dioxide and water. Simultaneously, sulfur dioxide is oxidized to sulfur dioxide, and nitric oxide is oxidized to nitrogen dioxide, both of which are sorbed by the sorbent constituent material, which is preferably intimately mixed on a microscopic scale with the oxidation catalyst. It is the invention that sulfur and NO _x compounds in the gaseous stream are removably connected in some manner to the catalyst / sorber system in an oxidizing atmosphere, and the invention is not intended to be limited to any particular mechanism proposed. Preferably, the sulfur and / or nitrogen compounds are removed from the catalyst system as a more concentrated stream of sulfur and / or nitrogen compounds than were present in the exhaust gas. Unless otherwise indicated, the percentages and ratios of the compounds are by weight.

Short description the drawings

1 FIG. 10 is a graph illustrating NO _x sorption from a simulation diesel exhaust using a single component catalyst system. FIG.

2 FIG. 10 is a graph illustrating NO _x sorption from a diesel engine exhaust using a two-component catalyst system. FIG.

3 Figure 3 is a schematic representation of an apparatus using a dual component catalyst system to remove NO _x and sulfur compounds.

4 Figure 9 is a graph showing NO _x sorption using a two component catalyst system in an in 3 illustrated device.

5 is a graph showing that the NO _x sorption using a catalyst system comprising a component and wherein the regeneration conditions are compared.

detailed Description sorption

The sorption step may be carried out at 37.8 to 537.8 ° C (100 to 1000 ° F), preferably at 148.9 to 371.1 ° C (300 to 700 ° F) at 200 to 200,000 h ^-1 GHSV, preferably 1,000 to 120,000 ^-1 . The pressure may range from below atmospheric pressure to 500 psig. GHSV, the gas hourly space velocity, is defined as a volume contaminated gas, measured at 21.1 ° C and 0.101 MPa, which can be processed by 0.028 m ^{3 of} catalyst in one hour.

In carrying out the process, as the sorbent reaches saturation, the concentration of nitrogen oxides and sulfur oxides in the exhaust gas from the catalyst begins to increase from undetectable to detectable levels. If the detectable fractions reach unacceptable levels, the exhaust gas flow is directed to a second bed of similar composition which starts the oxidation and sorption process.

Desorption / regeneration

For the two component catalyst system, the desorption step may be performed at 37.8 to 537.8 ° C (100 to 1000 ° F), lower temperatures of about 148.9 to 426.7 ° C (300 to about 800 ° F). however are preferred. The pressure may range from below atmospheric pressure to 500 psig. The velocity of the gas through the catalyst system during regeneration is GHSV 20 to 20,000 h ^-1 , preferably 50 to 10,000 h ^-1 .

It It is suggested that the spent catalyst sorbent by chemically reducing the nitrogen dioxide to nitrogen and the sulfur trioxide is regenerated to sulfur dioxide. This is achieved by the saturated Katalysososorptionsmittelverbund a second separate gas stream at a lower flow rate, containing an inert carrier and / or a reducing gas. The used regeneration gas contains Nitrogen and sulfur dioxide, which desorbs and purifies the system. After regeneration, the catalyst system is revitalized and will be back put into operation and the regeneration gas becomes another spent catalyst sorbent directed.

Especially important it was discovered that the reducing agent is fuel (diesel or gasoline), which is to drive the internal combustion engine is used. This is significant because a wheeled engine is not has to be transported to a separate regeneration reducing agent, like ammonia, if SCR were used.

Of Further, it was discovered that a premature degeneration of the catalyst / sorbent performance due to exposure to Sulfur oxide can be minimized or eliminated by adding a sulfur repellent System is used, consisting of a front bed of the catalyst / sorbent (Component a of the catalyst system with two components), which for sulfur oxides is specific, but not for Nitrogen oxides is active.

By doing the present sorption / desorption of the sulfur components in the feedstock will, can the sulfur compounds in the feed to between 5 to Be concentrated 100 times.

carrier

If A carrier for the Catalyst components is used, the carrier as ceramic or metallic monolith having a honeycomb body structure be characterized. Preferably, a carrier is used to prepare the catalysts, Distribute sorbers and modifiers. The ingredients are on the wearer in the wished conditions deposited. The composition of the ceramic carrier can an oxide or a combination of oxides. Suitable oxide carriers include the oxides of Al, Z, Ca, Mg, Hf, Ti and various mixtures from oxides such as cordierite and mullite.

The structure and composition of the carrier is very important. The structure of the support influences the flow patterns through the catalyst system, which in turn affects transport to and from the catalyst surface. The ability of the structure to act on the compounds to be catalyzed to transport to the catalyst surface affects the effectiveness of the catalyst / sorbent. The carrier is preferably macroporous with 64 to 600 cells (pores) per 6,452 ^cm2 (square inch) (cpsi) which (cm 2.54) (linear inch) (ppi) is about 25 to 80 pores per although carriers of 5 to 90 ppi are suitable.

Condition

The (a) catalyst component can be conditioned by repeating the sorption / desorption cycle. The amounts of sulfur ingredient released during this conditioning increase with each generation until it corresponds to the sorbed amount. It has been found that the conditioning time was dramatically reduced by permeating the catalyst / sorber with liquid H ₂ SO ₄ . For example, instead of 12 hours of conditioning after H ₂ SO ₄ treatment, only a few hours at 148.9 ° C (300 ° F) are necessary. The conditioning period also depends on the temperature at which the sorption and regeneration was carried out. By raising the temperature, the amount released can be increased, and therefore the conditioning time can be reduced. A spe No essential conditioning is necessary, since the catalyst / sorber is conditioned after a few cycles of sorption / regeneration and remains so.

Referring to 3 An apparatus using a two-component catalyst system for treating an exhaust gas is shown schematically. Preferably, at least two catalyst regions are used. There are two catalyst zones A and B, each containing a two-component catalyst system, 3A / 4A and 3B / 4B , Each catalyst region A and B is alternatively with the exhaust gas inlet 1 over the valve 2 and the wires 11 and 12 each near the areas 3A and 3B connected. The area 3A of region A contains the sulfur-selective catalyst, referred to as component (a), similarly contains the region 3B of region B, the sulfur-selective catalyst. The areas 4A and 4B contain a NO _x selective catalyst, designated as component (b). The wires 13 and 14 extend from the catalyst areas A and B and enter a valve 6 a, from which the exhaust gas discharge 7 extends. This describes the NO _x and sulfur removal structure of the device.

The regeneration assembly comprises a hydrocarbon source 8th which is the reducing agent / carrier and is at the valve 9 over the line 20 attached. The wires 21 and 22 are alternatively connected to the catalyst sections A and B respectively adjacent to the components (b). The wires 23 and 24 extend from the catalyst to the areas A and B respectively through the valve 10 to the line 25 resulting in a SO ₂ / H ₂ O sorption cartridge 11 and therefore to the regeneration gas outlet 12 leads.

The operation of the valves is preferably by an electronic sensor or sensors 17 in the exhaust outlet 7 determining, for example, a NO _x breakthrough indicating the need to regenerate the bed in question. A similar sensor or sensors 16 will, for example, determine an O ₂ increase to indicate that the regeneration of the bed in question is complete. Ideally, control units would 15 the valves 2 . 6 . 9 and 10 describe based on the determined constitution of the current in question. The regeneration operation should not be longer than the sorption operation because the exhaust gas inlet gas should be directed to the catalyst region having sulfur and NO _x sorption capacity. In situations where this is not the case, additional catalyst areas are necessary to always provide a regenerated area to receive the exhaust gas upon NO _x breakthrough in the presently deployed area.

In operation, the exhaust gas would be in the valve 2 over the line 1 enter and either to the line 11 or 12 be directed. In this illustration, the exhaust gas is via the line 11 into the catalyst zone (a) by first placing the sulfur-selective catalyst component (a) in bed 3A and then through the NO _x -selective catalyst component (b) in the bed 4A is directed and over the line 13 to the valve 6 and finally via the outlet line 7 exit.

Throughout the duration or part, a regeneration gas containing a reductant (as a gas) is released from the container 8th through the pipe 20 in the valve 9 which it passes through the line 22 into the catalyst region B, where it desorbs sulfur compounds and nitrogen compounds that were sorbed in an earlier sorption cycle. The desorbed gas enters in reverse flow direction in the exhaust gas and contacted by the first NO _x -selective catalyst component (b), and then the sulfur selective catalyst component (a) 3B ,

The sulfur in the regeneration gas is concentrated compared to the exhaust gas. The regeneration gas leaves the region B via the line 24 in the valve 10 , The administration 16 and the sulfur sorption cartridge 11 and over the line 12 out.

At a given time or when NO _x enters the catalyst region A, the valve becomes 2 conversely, to send the exhaust gas to the catalyst region B and the valve 6 is reversed while the regeneration gas in area B is stopped. Desirably, the regeneration gas will now pass through the valve 9 and the line 21 in the area A at 4A guided and the desorbed gas is from the area A via the valve 11 and the line 25 to the cartouche 11 and the exit 12 directed, wherein the cycle described is repeated continuously.

Examples

Component (a) of the catalysts / sorbers used in the examples were applied to one (200 cells per 6.452 cm ² -200 cells-per-square-inch) square cordierite honeycomb. The TiO ₂ / Pt washcoat was made by incipient wetness impregnation. The Pt content was between 0.1 to 2.2%. After drying and calcination at 500 ° C, the solids were dispersed in 7% acetic acid and ground overnight in a ball mill. The ceramic honeycombs were then dipped into the Washcoat / Pt slurry, removed, blown off and then dried at 150 ° C.

The Samples were subsequently added into a modifier solution dipped, removed, blown off and finally dried at 150 ° C. The catalyst / sorbent had a nominal composition as in Table 1 is shown on.

Table 1: Catalyst / sorbent composition (unless otherwise indicated):

For review were the samples into a 304 tubular stainless Filled steel reactor and introduced into a three-zone furnace. The reactor was with connected to a gas supply system, which supplied mixed gases, the simulated the exhaust gas of a gas turbine. The gases were by means of a Matheson Mass Flow Transmitter measured and controlled. Water was submerged in a preheat oven Using a Cole Palmer device Number 74900 introduced.

Example 1 (comparison)

A catalyst sorbent (single catalyst or component b) as taught in US Pat. No. 5,451,558 was prepared by placing a 200 cell per 6.452 cm ² (200 cells per square inch) cordierite honeycomb with 0.098 grams of high surface area Al ₂ O ₃ per cubic centimeter, 1 , 62 milligrams / cc Pt and 7.93 milligrams / cm ³ K ₂ CO ₃ . The catalyst core sample was introduced into a laboratory reactor for review. A simulated diesel exhaust was run at a space velocity of 30,000 per hour, 300 ppm NO _x , 900 ppm CO, 8.0% oxygen, 7.6% CO ₂ , 10.0% H ₂ O _2, and a temperature of about 260 ° C (500 ° F) used. The simulated exhaust stream did not contain sulfur compounds during this example.

The catalyst sorbent was subjected to a plurality of cycles of two minutes of oxidation / sorption followed by two minutes of reducing regeneration. The regeneration gas used was 9% methane in nitrogen at 260 ° C (500 ° F). The results of this experiment, which in the attached 1 show that the NO _x emission drops from 100 to less than 2 ppm at the beginning of a sorption cycle. The NO _x outlet increases during the 2 minute cycle until it reaches a final value of approximately 30 ppm. The initial NO _x inlet value prior to each sorption cycle is also provided. The mean NO _x disruption efficacy obtained during this study was still 95%.

Example 2

A catalyst system was prepared by placing two catalysts / sorbers in series. The anterior segment (component a) was prepared by incubating one 200 cells per 6.452 cm ² (200 cells per 6.452 square inches) of cordierite honeycomb structure with 0.122 grams / cc TiO ² and 1.84 milligrams / cm ³ Pt and 10.0 milligrams / cm ³ CO (O) was coated as described above and in US Patent Application 09 / 113,258, which is fully incorporated herein. Component (b) was prepared as in Example 1.

One Part of a diesel exhaust produced by a 4-cylinder turbo-assisted engine with a displacement of 3.9 liters using No. 2 diesel fuel was filtered and passed through a laboratory reactor and the two catalysts / sorbers in series (component a followed by component b). Various Loads were transferred to the engine an electric generator while maintaining a constant engine speed of 1,900 rpm was maintained.

The Diesel exhaust gas composition is shown in Table 1 for each Motor loads shown.

Table 2 Diesel engine exhaust gas compositions under various loads

Investigations were carried out at a space velocity of 12,000 hr ^-1 . The catalyst was regenerated with 2% H ₂ gas in a nitrogen carrier at a space velocity of 2,000 hr ^-1 . The regeneration flow direction was opposite to the exhaust flow direction.

The average catalyst temperature was 371.1 ° C (700 ° F) during this run. The NO _x outlet concentrations are in 2 as a function of time for the engine loads shown in Table 2. The length of time over which the catalyst system effectively removes NO _x decreases with increased inlet concentration of NO _x . Table 3 shows the duration of time over which the catalysts remove more than 90% NO _x for each load and NO _x inlet concentration. The SO 2 in the diesel exhaust was captured by component (a) of the two-bed system during the oxidation mode and released as SO ₂ into the regeneration flow stream.

Table 3 Duration for more than 90% NO _x removal for different NO _x inlet concentrations.

Example 3

The twin bed system described in Example 2 was tested in a laboratory reactor with a simulated exhaust gas having a composition of 70 ppm NO ₂ , 10 ppm CO, 3.05% CO ₂ , 10% H ₂ O and 14.5% O ₂ in nitrogen , The oxidation sorption cycle was carried out at 315.6 ° C (600 ° F), a space velocity of 30,000 hr ^-1 for 15 minutes.

During the oxidation / sorption, the catalyst system removed the NO _x to unreachable levels when the catalyst sorptive sites were filled, increasing the emitted NO _x concentration to a final level of 12 ppm. The effectiveness of NO _x removal was 96.5%. At the end of the oxidation sorption cycle, regeneration was accomplished with vapor phase # 2 diesel. The regeneration with diesel fumes was carried out by introducing the liquid diesel into the hot nitrogen stream. The regeneration gas was then passed to the spent catalyst / sorber in a low direction opposite to the simulated gas. The flow rate of the diesel, which was necessary for the regeneration was 0.005 cm ³ / min. the liquid diesel; Regeneration occurred at a space velocity of 3,500 hr ^-1 for 3 minutes. 3 minutes were sufficient for a complete regeneration. Therefore, 0.41 g of diesel per gram of NO _x (as NO ₂ ) was needed to convert NO _x to N ₂ . Subsequent oxidation / sorption cycles showed a fully revitalized catalyst.

Example 4

A two-chamber construction was like in 3 shown constructed. The catalyst system composition and structure used were the same as in Examples 2 and 3. Diesel exhaust was produced by a 4-cylinder turbo-assisted engine with a displacement of 3.9 liters; the fuel was # 2 diesel. A 48% load was applied to the engine via an electric generator while a constant speed of 1,900 rpm was kept. All engine exhaust was passed over a catalyst at a space velocity of 11,800 hr ^-1 . No particulate filter was used to remove the particulate matter from the exhaust gas before the catalyst.

The average exhaust gas inlet temperature into the catalyst was 273.9 ° C (525 ° F). The catalyst was operated between the engine exhaust stream for 5 minutes and a regeneration gas for 5 minutes. The regeneration gas consisted of 14% H ₂ in nitrogen at a space velocity of 220 hr ^-1 . The catalyst removed 98.9% of the NO _x inlet over a 50 minute test period. This is in 4 shown.

Example 5

Examples 2, 3 and 4 used a two-bed catalyst / sorbent system. This design was desirable to prevent excessive exposure of sulfur dioxide to the second bed. It was shown that the Pt / Al ₂ O ₃ / K ₂ CO ₃ system described in Example 1 was more difficult to regenerate when exposed to excess sulfur oxide. A catalyst prepared by coating a 200 cells per 6.452 cm ² (200 cells per square inch) cordierite honeycomb structure coated with 0.122 grams / cm ³ TiO 2, 1.84 milligrams / cm Pt, and 7.93 milligrams / cm ³ NA ₂ CO ₃ regenerated more easily when exposed to sulfur oxides.

In this example, a single bed of the TiO ₂ / Pt / Na ₂ CO ₃ catalyst / sorber was introduced into a laboratory reactor and subjected to an oxidizing sorption cycle with a simulated exhaust gas mixture containing 70 ppm NO _x , 50 ppm CO, 3.05% CO ₂ , Exposed to 10% H ₂ O and 14.5% O ₂ in nitrogen. The run was performed at 315.6 ° C (600 ° F) at a space velocity of 22,500 hr ^-1 .

The results showed that all the carbon monoxide was oxidized to carbon dioxide by contact with the catalyst. The NO _x -Auslassanteile are 5 shown as a function of the exposure duration. After about 5 minutes after the catalyst was exposed to the simulated exhaust gas flow, the NO _x outlet concentration (curve a) began to increase and reached a value of about 3.8 ppm after a 14 minute exposure. After each oxidation sorption cycle, regeneration is performed using 2% methane in nitrogen at 315.6 ° C (600 ° F).

As well as in 5 shown, the NO _x emissions are obtained after two more cycles with simulated exhaust gas flow, but 30 ppm sulfur dioxide was added to the simulated exhaust gas flow (curve b). The data shows that catalyst performance is reduced over NO _x removal with extended use. This effect results from the consumption of the sorption sites by the formation of Na ₂ SO ₄ on the catalyst surface, which is not destroyed during the regeneration at 600 ° F.

The catalyst sample was then subjected to the same regeneration flow as before, but during this regeneration cycle the temperature was raised to 443.3 ° C (830 ° F). The values obtained during this regeneration showed the removal of sulfur from the catalyst surface with a release of both SO ₂ and H ₂ S.

After the high temperature exposure to the regeneration gas, the reactor was cooled to 315.6 ° C (600 ° F) and another sample was run using the simulated exhaust gas stream. The values of this test are also in 5 represented (curve c). The catalyst now acted as during the initial test against exposure to sulfur dioxide-containing streams.

in the Generally, the gas to be treated is referred to herein as "exhaust", which a preferred use for the present catalyst system, method and apparatus is however, gas can be used from any source and the term "exhaust" is meant to be all sources include.

Claims (35)

A process for the removal of gaseous sulfur compounds and / or NO _x , comprising contacting discrete beds of a gaseous stream comprising gaseous sulfur compounds and / or NO _x with a catalyst system comprising (a) a catalyst / sorber comprising a noble metal catalyst component Metal oxide sorbent component, a modifier consisting of oxides of Ag, Cu, Bi, Sb, Sn, As, In, Pb, Au or mixtures thereof and (b) a material comprising an oxidation catalyst selected from platinum, palladium, rhodium, cobalt, nickel, iron , Copper, molybdenum or combinations thereof deposited on a high surface area support, an absorber material selects from a hydroxide, carbonate, bicarbonate of an alkali or alkaline earth or mixtures thereof under conditions to remove and retain the gaseous sulfur compound and / or NO _x from that stream into the catalyst system to allow a reduction in capacity in that system to remove and retain the sulfur and / or NO _x compounds; and then regenerating the catalyst system comprising contacting the catalyst system with a regeneration gas under conditions to remove the retained sulfur and / or NO _x compounds, the regeneration gas comprising a reducing gas, a portion of the capacity of the catalyst system for removal and retention of the catalyst system Sulfur compounds and NO _{x is} restored. The method of claim 1, wherein the gaseous stream containing the gaseous sulfur compounds and / or NO _x flows in a first direction and the regeneration gas flows in a second direction opposite to the first direction. The method of claim 2, wherein gasoline in the regeneration gas is available. The method of claim 2, wherein diesel is in the regeneration gas is available. The process of claim 1, wherein the (a) catalyst / sorber Pt and supported by a ceramic oxide. The method of claim 5, wherein Pt is 0.005 to 0.05 Grams per cc of the noble metal catalyst component and a metal oxide ore component includes. The method of claim 1, wherein the noble metal catalyst component of (a) comprises Pt, Pd, Rh, Ru or mixtures thereof. The method of claim 1 wherein the metal oxide sorbent component from (a) is an oxide of Ti, Zr, Hf, Ce or mixtures thereof. The method of claim 7 wherein the metal oxide sorbent component from (a) is an oxide of Ti, Zr, Hf, Ce or mixtures thereof. The method of claim 1, wherein the modifier of (a) Cu, Ag, Bi or mixtures thereof. The method of claim 9, wherein the modifier of (a) is an oxide of Cu, Ag, Bi or mixtures thereof. The method of claim 11, wherein the modifier of (a) Cu oxide. The method of claim 11, wherein the modifier of (a) Ag oxide. The method of claim 11, wherein the modifier of (a) Bi oxide. The method of claim 1, wherein the regeneration gas an inert carrier and a reducing ingredient. The method of claim 15, wherein the inert gas Nitrogen, helium, argon or steam is. The process of claim 16, wherein the reducing ingredient is hydrogen, methane, hydrocarbons of C ₁ to C ₁₂ or mixtures thereof. The method of claim 1, wherein the regeneration gas Oxygen includes. Catalyst system comprising separate beds (a) a catalyst / sorbent comprising a noble metal catalyst component, a metal oxide sorbent component, a modifier consisting of oxides of Ag, Cu, Bi, Sb, Sn, As, In, Pb, Au and mixtures thereof and (b) a material comprising an oxidation catalyst selected from Platinum, palladium, rhodium, cobalt, nickel, iron, copper, molybdenum or their Combinations deposited on a high surface area support, one Absorber material selected from a hydroxide, carbonate, bicarbonate of an alkali or alkaline earth or mixtures thereof. The catalyst system of claim 19, wherein the noble metal catalyst component from (a) comprises Pt, Pd, Rh, Ru or mixtures thereof. The catalyst system of claim 20, wherein the metal oxide sorbent component from (a) is an oxide of Ti, Zr, Hf, Ce or mixtures thereof. The catalyst system of claim 21, wherein the modifier of (a) Cu, Ag, Bi or mixtures thereof. The catalyst system of claim 22, wherein the modifier of (a) Cu oxide. The catalyst system of claim 22, wherein the modifier of (a) Ag oxide. The catalyst system of claim 22, wherein the modifier of (a) Bi oxide. A catalyst system according to claim 20, wherein the platinum, Palladium, rhodium, cobalt, nickel, iron, copper, molybdenum or combinations from (b) 0.005 to 0.05 grams per cc of the total oxidation catalyst and absorber material. The catalyst system of claim 26, wherein the high surface area support is (b) Al ₂ O ₃ , TiO ₂ , ZrO ₂ , SiO _2, or mixtures thereof. The catalyst system of claim 27, wherein the alkali or alkaline earth metal of (b) 0.000005 to 0.02 grams per cc of the total Oxidation catalyst and absorber material comprises. The catalyst system of claim 28, wherein the metal oxide sorbent component from (a) an oxide of Ti, Zr, Hf, Ce or mixtures thereof. The catalyst system of claim 29, wherein the modifier of (a) Cu oxide. Device comprising: A. An exhaust treatment arrangement (full): (1) at least two catalyst zones, each Catalyst zone contains a catalyst system comprising separate beds from (a) a catalyst / sorber comprising a noble metal catalyst component, a metal oxide sorbent component, a modifier consisting of Oxides of Ag, Cu, Bi, Sb, Sn, As, In, Pb, Au or mixtures thereof and (b) a material comprising an oxidation catalyst selected from Platinum, palladium, rhodium, cobalt, nickel, iron, copper, molybdenum or their Combinations deposited on a high surface area support, one Absorber material selected from a hydroxide, carbonate, bicarbonate of an alkali or alkaline earth or mixtures thereof (2) a main exhaust inlet pipe connected With (3) an exhaust inlet valve (4) a separate secondary exhaust gas inlet line from the exhaust inlet valve adjacent to the (a) bed each of the catalyst zones, (5) a separate secondary exhaust outlet conduit, which extend from each of these catalyst zones adjacent to (b) This bed extends and is connected with (6) an exhaust gas outlet valve connected to a main exhaust passage, which differs from the Exhaust outlet valve extends, with a steam flow path through each the catalyst zones through both separate beds from the inlet is present to the outlet in an arrangement; and a regeneration arrangement comprising: (1) one Main regeneration gas inlet line connected to (2) one Regeneration gas valve, (3) a separate secondary regeneration gas inlet line from the regeneration gas inlet valve connected to each of the catalyst zones, connected to the (b) beds of these, (4) a separate one secondary Regeneration gas outlet, different from each of the catalysts on the (a) bed of which extends and is connected to (5) a regeneration gas outlet valve and (6) a main regeneration gas exhaust pipe, which extends from the regeneration gas outlet valve. A method of treating a gaseous stream containing gaseous sulfur compounds and / or NO _x compounds in an apparatus according to claim 31 comprising the steps of: A. a treatment cycle comprising: (1) supplying a gas containing gaseous sulfur compounds and / or NO _x (2) adjusting the exhaust gas inlet valve to a first catalyst zone in contact with the catalyst system, (3) passing the gas containing gaseous sulfur compounds and / or NO _x compounds through the secondary exhaust gas inlet pipe to the exhaust gas inlet line first catalyst zone for first contacting the (a) bed and exhausting the exhaust gas flow from the first catalyst zone through the second exhaust outlet conduit to the exhaust valve, (4) the exhaust outlet valve being set to connect to the main exhaust outlet conduit; Exhaust gas inlet valve and the Abgasausl intake valve from the first catalyst zone to another catalyst zone, wherein the supply of the gas containing the gaseous sulfur compound and / or NO _x compounds is terminated; and a regeneration gas cycle after the treatment cycle full: (1) Feeding a regeneration gas through the main regeneration line to the regeneration gas valve, (2) adjusting the regeneration gas valve, to contact the first catalyst zone and pass of the regeneration gas through the secondary regeneration gas line to the first catalyst zone to contact the (b) first bed, (3) Withdrawing the regeneration gas from the first catalyst zone the second regeneration gas line too (4) the regeneration gas valve, which is set to deal with the main regeneration gas line connect to. The method of claim 32, wherein the treatment cycle and the regeneration cycle repeated.